1. Field of the Invention
The present invention is generally related to low biofouling filtration membranes, and more particularly to graft branched polymers or copolymers containing zwitterionic groups on fluorine-based filtration membranes or films for the purpose of anti-biofouling.
2. Description of the Prior Art
Proteinaceous biomolecules are highly complex, containing both hydrophilic and hydrophobic regions. These biomolecules are highly conformable and adaptable toward adsorption to surfaces having hydrophobic moieties thereat. Therefore, many hydrophilic surfaces are used to reduce protein adsorption. However, these surfaces are often not sufficient to prevent the undesirable adhesion of cells, bacteria, or other microorganisms. Even a small amount of proteins on a surface can lead to the adhesion and propagation of unwanted fouling. For example, fibrinogen adsorption less than 5-10 ng/cm2 is needed to inhibit platelet adhesion for blood compatibility, and superlow fouling surfaces are required for these applications.
However, only a few candidates are regarded as “nonfouling materials” or “superlow fouling materials”. Poly(ethylene glycol) (PEG) or oligo(ethylene glycol) (OEG) modified surfaces have been extensively studied to resist protein adsorption. The steric exclusion effect was considered as one of the reasons for PEG polymers to resist protein adsorption. However, PEG or OEG group decomposes in the presence of oxygen and transition metal ions found in most biochemically relevant solutions.
Phophorylcholine (PC)-based polymers or surfaces have been shown to decrease protein adsorption. They are considered as biomimetic fouling-resistant materials since they contain phosphorylcholine headgroups, which are found in the outside layer of cell membranes. The hydration of PC-based materials is also thought to be the reason for their resistance to protein adsorption. However, it is desirable to develop new materials other than PC for applications requiring long-term material stability due to the tendency of the phosphoester group to be hydrolyzed. In addition, PC monomers, such as 2-methacryloyloxyethyl phosphorylcholine (MPC), are moisture sensitive and not easy to synthesize and handle.